JPS60218336A - Liquid-phase hydrogenation of 3c fraction - Google Patents

Abstract

PURPOSE:The feed of hydrogen is divided into 3 or more stages to effect the liquid-phase hydrogenation of the 3C fraction in the presence of a catalyst by staircase reactions to increase the efficiency of the reaction. CONSTITUTION:The liquid-phase hydrogenation of the 3C fraction containing, as major components, propylene and propane and, as trace components, propadiene and methylacetylene is carried out by dividing the hydrogen feed into 3 or more stages at 0-100 deg.C under a pressure of 5-20 atmospheric pressure to give propylene free from propadiene and methylacetylene. The hydrogen feed at the first stage is adjusted in molar ratio calculated as pure hydrogen, to less than 1.0 to the total amounts of propadiene and methylacetylene in the 3C fraction. EFFECT:The process can inhibit propylene from being converted into propane by side-reactions, when a trace amount of propadiene and methylacetylene is converted into propylene with hydrogen.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention 8A is used to remove pro-1, padiene, and methylacetylene, which are trace components in the so-called Cs fraction, which mainly consists of propylene and prono-kun.・So-called liquid-phase water vapor method for Cs fraction, in which the Os fraction is reacted with externally supplied hydrogen in the presence of a catalyst in the liquid phase, more specifically, the hydrogen necessary for the Cs fraction. This invention relates to a method for suppressing the conversion of siglobifune to propane due to a side reaction when glopadiene and methylacetylene react with hydrogen to convert into propylene, by supplying amounts in three or more stages and causing the reactions to occur sequentially. It is something.

[Technical background]

Various methods are known for producing propylene, which is one of the key petrochemical products, but the majority of the production is based on the steam cracking of petroleum fractions such as naphtha, which produces various products such as ethylene. It is often produced in one way, ie in a so-called ethylene plant.

In ethylene plants, crude gas containing many types of hydrocarbon compounds obtained by cracking petroleum fractions such as naphtha is separated according to carbon number by pressurized distillation in the first stage of purification. The fraction containing the compound having 6 carbon atoms thus obtained is called a Cs fraction.

This 03 fraction is further purified to obtain propylene as a product.

In addition to propylene, which accounts for more than 90 percent by weight, this Cs fraction also contains glopadiene, which accounts for 5 to 2 percent by weight, methylacetylene, which accounts for about the same amount, and propane, which accounts for the remaining majority.

Although there is a method of isolating globadiene and methylacetylene, the mainstream method is to convert them into propylene through a so-called selective hydrogenation reaction in which they are reacted with hydrogen. A catalyst is generally used in the hydrogenation reaction of the Cs fraction. In this case, an alumina or silica-alumina carrier supported with palladium, platinum, or the like can be used. The catalyst used may be a commercially available one or a specially prepared one. The performance characteristics of these catalysts are such that they selectively promote the reaction between globadiene and the like and hydrogen over the coexisting reaction between propylene and hydrogen, and are therefore called selective hydrogenation catalysts. The reason why the selectivity of the reaction is important is obvious considering that the reaction of propylene with hydrogen means the disappearance of propylene and the production of the same molar amount of propane, and considering the market situation where propylene is more expensive than propane.

Next, as a reaction method, there are a liquid phase method and a gas phase method depending on the phase of the Cs fraction during the reaction. Since this reaction is an exothermic reaction, there are two types of reactors: isothermal reactors equipped with a heat removal device and adiabatic reactors not particularly equipped with a heat removal device.

The reaction conditions are 0 to 100°C under a pressure of 5 to 20 atm.
It is generally carried out within the temperature range of . The combination of temperature and pressure is determined by also taking into consideration the gas-liquid equilibrium conditions of the Cs fraction.

The choice between the liquid phase method and the gas phase method is made based on the overall circumstances of the propylene n manufacturing process, including before and after the hydrogenation equipment. If it is advantageous to use a liquid phase before and after the hydrogenation equipment, the liquid phase method is advantageous unless technical problems are taken into consideration. In this case, the vapor phase method requires extra vaporization equipment and condensation equipment, which increases operating costs.

One of the technical issues in the liquid phase process is the development of a highly selective catalyst and its operating method. The operating temperature of the gas phase method is usually in the range of 40 to 100°C for existing catalysts, but
In this temperature range, the liquid phase method exhibits a significant decrease in selectivity and an increase in the amount of propylene consumed. For this reason, in the liquid phase method, the reaction temperature is often carried out at 10° C. or lower.

In order to carry out the reaction in this temperature range, it is necessary to remove the heat generated by the reaction and, depending on the conditions of the feedstock, use a cooling device for preliminary cooling. You will need something. Therefore, refrigeration equipment is required to supply the refrigerant, and its operating cost is much higher than that of a general-purpose cooling water supply system.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned current situation, and its purpose is to provide an improved liquid phase hydrogenation method for Cs fraction.

[Structure of the invention]

The present invention is a liquid phase hydrogenation method for a Cs fraction, which is characterized in that when hydrogenating a Cs fraction in the liquid phase in the presence of a catalyst, hydrogen is supplied in multiple stages of five or more stages.

Regarding the liquid phase hydrogenation method of Cs fraction, the present inventors have found that high selectivity can be achieved within a temperature range that can be achieved by cooling using general-purpose cooling water, specifically, at a reaction temperature in the range of 20 to 100°C. The present invention was completed as a result of various exploratory research conducted in order to develop a catalyst and its operating method. In other words, by using a conventionally used hydrogenation catalyst and supplying hydrogen in multiple stages of five or more stages, side reactions are reduced and the efficiency is increased by selectively hydrogenating the <Os fraction in the liquid phase. I found out.

The present invention will be explained in detail below.

First, "hydrogen ratio" will be explained as a variable for explaining reaction conditions. For the Cs fraction and crude hydrogen gas involved in the reaction, their streams.

Calculated from the basin and composition, the ratio of the molar flow rate in terms of pure hydrogen to the sum of the molar flow rates of globadiene and methylacetylene is defined as the hydrogen ratio. From the definition, if the hydrogen ratio is less than 1.0, the entire amount of propadiene etc. will not react and some of it will necessarily remain. This reaction can be expressed as follows.

03H4+ xH, -+ xcHH6+ (1-x)
(1!3H4 However, 0 (x (1) When the hydrogen ratio is 1.0, if no side reactions occur, the entire amount of fluoracienes, etc. will react to produce equimolar propylene, and the entire amount of hydrogen will be consumed. Expressed as a formula, it is as follows.

0sH4+xa, →x03H.

However, if the x = 1 hydrogen ratio exceeds 1.0, even if the entire amount of fluoraciene etc. reacts, the hydrogen will always be hydrogen with a metal surplus of 140
Reacts with propylene in the x fraction to convert the propylene to propane. If the hydrogen ratio is further increased, this excess frozen confection will also increase and the amount of propylene conversion will increase. This reaction can be expressed as follows.

03H4+xH1+(:+c-1)03H,1-+xo
3H@+(x-1)Hl-+(x-1) CIIHII
+03H, however! >1 or more, in order to completely remove fluoracienes, etc., considering the reaction rate, etc.
Among the reaction conditions, it is necessary to operate at a hydrogen ratio of 1.0 or more, but it can be said that the closer it is to 1.0, the higher the propylene yield.

Next, the progress of the experiment conducted by the present inventors will be explained. The reactor used in the experiment had an inner diameter of s, ocPn, and a height of 2. A double Om cylindrical tube with a structure that allows cooling water to pass through the outer tube was used. A schematic diagram of the experimental setup is shown in FIG. Regarding the catalyst,
0.05 in weight percent relative to the activated alumina of the support.
Palladium of α45 to α45 was prepared and used.

The operating method of the reactor will be explained with reference to FIG.

Filled with catalyst, Taaoki IK valve, and more. 3 Supply 1. The crude hydrogen passes through valve 5 and is further divided into valves 4,
It is fed to the reactor through valves 5, 6, 7 and 8.

The reaction liquid is discharged through valve 97. Reactor outer tube 1
Cooling water at a temperature of 20 to 35° C. is kept flowing through the 0 at all times. For analysis of the reaction solution, a small amount of the reaction solution was sampled using sample valves 11, 12, 15, 14, and 15, and its composition was analyzed by gas chromatography. Temperature measurement inside the reactor was automatically recorded by installing temperature measurement terminals in each part.

Example 1 The experimental apparatus shown in Figure 1 was filled with 50 kg of catalyst supported with 0.50 weight percent palladium, and the apparatus was charged with C3.
Distillation 25.7 hours (595 f-mol/hour) and purity 94.
5 mol percent of crude hydrogen (94.5 mol of hydrogen, 5.5 mol % of methane) was fully supplied and the pressure was 19.0 XZ/cr.
n''G.The hydrogen supply division method was changed to supply C3.
When expressed as a hydrogen ratio based on the molar flow rate of fluoracienes, etc. in the fraction, the first stage was α9, the second stage was [L2], and the third stage was Q, 15. At this time, the cumulative amount of hydrogen supplied to each stage is the hydrogen ratio, [19-1, 1-1, 2
It becomes 5. Note that the inlet temperature of the cooling water was 29°C, and the outlet temperature was 30°C.

Other experimental conditions and results are shown in Table-1.

Example 2 An experiment was conducted using the same equipment, catalyst, C3 fraction of the same composition, and crude hydrogen as in Example 1. When the hydrogen supply division method is shown using the same standard hydrogen ratio as in Example 1, the first stage is α7, the second stage is α7, and the second stage is α7.
The number of rows was set to 0.2, the third row 0.2, the fourth row 11L1, and the fifth row 0.05. That is, the cumulative amount of hydrogen supplied to each stage is the hydrogen ratio, α7- (L 9-1.
Table 2 shows the results of a test conducted under the same conditions as 1-1.2-1.25 except for the conditions shown in Table 2.

Comparative Example An experiment was conducted using the same equipment, catalyst, 03 fraction of the same composition, and crude hydrogen as in Example-1. The method of dividing the hydrogen supply was such that the hydrogen ratio was 1.0 in the first stage and 0.25 in the second stage based on the same standard hydrogen ratio as in Example 1. That is, the test was conducted under the same conditions except for the conditions shown in i-2, under the conditions that the cumulative amount of hydrogen supplied at each stage was 1.0.1.25 in terms of hydrogen ratio.

The experimental conditions and results are shown in Table-5.

As can be seen from Table 1, Table 2 and Table 3 showing the results of Examples and Comparative Examples, the reaction temperature was in the range of 20 to 50°C.
When carrying out liquid phase hydrogenation of a fraction (1) In the partial supply of hydrogen, it is possible to maintain high reaction selectivity by setting the hydrogen ratio in the first stage to less than 1.0, preferably less than a, 8. can. That is, the removal efficiency of glopadiene and the like is high, and the conversion of propylene to propane is small.

(2) Regarding the supply of hydrogen to the second and subsequent stages, the reaction selectivity can be kept higher as the hydrogen is divided into smaller portions and supplied in multiple stages.

(3) When hydrogen is supplied in the first stage at a hydrogen ratio of 1.0 or more, the reaction selectivity decreases to a considerable extent.

(4J When removing glopadiene, etc. with a hydrogen feed divided into two parts or less, the removal efficiency decreases and the conversion of propylene to propane increases significantly.

[Brief explanation of drawings]

The drawing is a schematic diagram of a liquid phase hydrogenation experimental apparatus in the present invention. 1. Reactor, 2. Raw material supply valve, 3.4.5.6.7
．． 8.Hydrogen supply valve, 9.Reaction liquid discharge valve, 10.Reactor outer tube, 11.12.13.14.Sample collection valve Patent applicant: Osaka Petrochemical Co., Ltd. Agent Hirodo Nakamoto Shodo Kami. Ryo Katsui

Claims (1)

[Claims] 1. Liquid-phase water of a Cs fraction, characterized in that hydrogen is supplied in multiple stages of three or more stages during hydrogenation reaction of the Cs fraction in the liquid phase in the presence of a catalyst. Addition method. 2. The method according to claim 1, wherein the hydrogen supply in the first stage is at a molar ratio of less than 1.0 in terms of pure hydrogen with respect to the total amount of globadiene and methylacetylene in the Cs fraction.